1. Field of the Invention
The present invention generally relates to an optical pulse generator and an optical pulse tester that is operated using the optical pulse generator.
Priorities are claimed on Japanese Patent Applications No. 2006-267992, filed Sep. 29, 2006, No. 2006-267993, filed Sep. 29, 2006, and No. 2007-179505, filed Jul. 9, 2007, the contents of which are incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
An optical pulse tester is a device that is configured to test the performance of an optical fiber such as transmission loss and point of failure. The optical pulse tester is configured to cause an optical pulse to be incident into a test target, for example, an optical fiber, and to detect backscattered light that has been given by the optical fiber, thereby testing the performance of the optical fiber. The optical pulse tester may also be called to as “optical fiber tester” or “optical time domain reflect meter”. The optical pulse tester may typically use an optical pulse generator. The optical pulse generator may include a laser diode and a driver circuit. The laser diode is driven by the driver circuit so that the laser diode emits optical pulses.
Japanese Unexamined Patent Application, First Publication, No. 2000-283884 discloses a conventional optical pulse tester and an optical pulse generator used for allowing the optical pulse tester to perform the test.
Japanese Unexamined Patent Application, First Publication, No. 6-201482 discloses another conventional optical pulse tester and an optical pulse generator used for allowing the optical pulse tester to perform the test.
One of the most important performance factors for the optical pulse tester is the spatial resolution thereof. The spatial resolution is the ability to distinguish the scattering point on the optical fiber with reference to the optical pulse generator. In other words, the spatial resolution is the ability to distinguish the distance of the scattering point from the optical pulse generator over the optical fiber. In general, the spatial resolution is increased by increasing the abruptness of the rising and/or falling edges of a pulse and also by narrowing the pulse width.
The conventional optical pulse generator has a closed-loop connection of a switching transistor, a voltage generator, and a laser diode. The switching transistor is driven to be switched ON and OFF by a pulse control signal. In a case, the switching transistor may be a high speed switching transistor that has high speed switching performance. The high speed switching transistor or the peaking circuit can be used to increase the abruptness of the rising and/or falling edges of an optical pulse and/or to narrow the optical pulse width. However, further increase in the abruptness of the rising and/or falling edges of an optical pulse and/or further narrowing of the optical pulse width are necessary for advanced optical pulse generators.
The conventional optical pulse generator generates optical pulses that have a low peak to peak value of optical pulses, resulting in narrow dynamic range of the optical pulses.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved an optical pulse generator and an improved optical pulse tester that is operated using the improved optical pulse generator. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.